Kerosene compositions

ABSTRACT

A method of controlling the odour emitted by a kerosene composition such that it is below a specified level, by ensuring that the composition has the following properties: (1) the range from initial boiling point to end point, in accordance with the atmospheric pressure distillation test method stipulated in JIS K2254, is in the range of 140° C. to 300° C.; (2) the density is 0.81 g/cm 3  or less; (3) the aromatic hydrocarbon content is 0 to 20% by volume; (4) the sulphur content derived from benzothiophenes and dibenzothiophenes is 0 to 50 ppm by mass; and (5) the fraction at 250° C. and above is 0 to 20% by volume; and such a kerosene composition.

This application claims the benefit of Japanese Patent Application 2004-342501 filed Nov. 26, 2004 under 35 USC §119(a).

The present invention relates to kerosene compositions, particularly for heating or cooking purposes.

Kerosene is widely used for heating purposes and cooking purposes. However, it has the drawback, particularly when used in open-type space heaters such as portable heaters or fan heaters, or when used in oil-burning cooking stoves, or when used in domestic boilers, that incomplete combustion occurs at the time of ignition or extinction, and an unpleasant odour arises due to the unburned hydrocarbons which are produced at this time.

But the levels of safety and comfort (low generation of NOx, hydrocarbon compounds, CO, SO₂, etc. and no accompanying unpleasant odour) required by users of kerosene heaters has been increasing year by year.

Furthermore, there is an increasing demand, as there is with regulations relating to exhaust emissions from cars, for products which put a low burden on the environment when using space heaters that exhaust indoors.

Under these circumstances, kerosene as used in oil-burning space heaters must also be in the form of products that can comply adequately with the requirements of users.

Among methods to resolve the generally recognised drawback of kerosene, in that it has an unpleasant odour when ignited, during normal combustion and upon extinction, a method of using a kerosene vaporisation catalyst, as described in JP-B-59-16814, and a method of adding a deodorant to the kerosene, as described in JP-B-54-32003, have been proposed.

However, with the method in which a kerosene vaporisation catalyst is used, the catalyst degrades with time and so it has been difficult to maintain clean combustion and low odour combustion for long periods. Furthermore, the method in which a deodorant is added to the kerosene has not been very effective because of the problem that individual preferences for fragrances vary.

The present invention is concerned with a kerosene composition with good combustion properties and in which the exhaust gases are clean, particularly in that the amounts of unburned hydrocarbons and sulphur oxides in the exhaust gases are low and the odour is improved.

The present invention provides a kerosene composition with a density and aromatic hydrocarbon content below specified limits, and preferably also an odour index, as expressed by a stipulated formula, below a specified limit.

In the following description, “JIS” relates to the Japanese Standards Association.

In accordance with the present invention there is provided a method of controlling the odour emitted by a kerosene composition such that it is below a specified level, which method comprises ensuring that said composition has the following properties:

-   (1) the range from initial boiling point to end point, in accordance     with the atmospheric pressure distillation test method stipulated in     JIS K2254, is in the range of 140° C. to 300° C.; -   (2) the density is 0.81 g/cm³ or less; -   (3) the aromatic hydrocarbon content is 0 to 20% by volume; -   (4) the sulphur content derived from benzothiophenes and     dibenzothiophenes is 0 to 50 ppm by mass; and -   (5) the fraction at 250° C. and above is 0 to 20% by volume.

Preferably, said kerosene composition has a bromine index of 65 Br₂mg/100 g or less.

More preferably, said kerosene composition satisfies the following odour formula (T formula): 10 Log{[4D+6(BT+DBT)+20A+Or+4T₂₅₀]/(0.01S)}≦_(—)84.0 where:

-   Log is a natural logarithm; -   D is the density of the kerosene composition (g/cm³); -   BT is the sulphur content derived from benzothiophenes in the     kerosene composition (ppm by mass); -   DBT is the sulphur content derived from dibenzothiophenes in the     kerosene composition (ppm by mass); -   A is the aromatic hydrocarbon content of the kerosene composition (%     by volume); -   Or is the bromine index of the kerosene composition (Br₂ mg/100 g     after conversion to bromine); -   T₂₅₀ is the amount of distillate at 250° C. or more in the kerosene     composition, in accordance with the atmospheric pressure     distillation test method stipulated in JIS K2254 (% by volume); and -   S is the smoke point (mm).

The present invention will be described in more detail below.

In accordance with the method of the present invention, the kerosene composition of the present invention is prepared so as to have the aforementioned properties by synthesising kerosene products or gases obtained by refining crude oil, and then using the synthetic kerosene products thus prepared or mixtures thereof.

The kerosenes obtained by refining crude oil include all kerosenes produced from crude oil, for example straight-run desulphurised kerosenes, where the kerosene fraction is extracted in an atmospheric distillation apparatus and the sulphur content is removed in a sulphur-removal apparatus, pyrolysis kerosenes, hydrocracked kerosenes, and so on, provided the distillation range is 140 to 300° C. or less.

The kerosene compositions of the present invention can be obtained by taking synthesis gas obtained by the partial oxidation, steam reforming, etc. of natural gas or coal, for example, forming a long chain alkyl hydrocarbon polymer oil by means of a Fischer-Tropsch reaction and then carrying out hydrocracking and distillation to prepare a material with the prescribed properties. Furthermore, they can be obtained by cracking or synthesis, for example, from the various fractions which are obtained in petroleum refining.

In addition to natural gas or coal, such Fischer-Tropsch products also may be derived from natural gas liquids, petroleum or shale oil, petroleum or shale oil processing residues, or biomass.

The odour when kerosene is burnt in oil-burning apparatus is inferred to be due mainly to unburned hydrocarbons and the sulphur content in the combustion exhaust gases. More specifically, it is believed that it is due to unburned aromatic hydrocarbons/olefins and sulphur oxides and also unregulated compounds which are being investigated also in the case of car exhaust emissions (including aldehydes, benzene, toluene, xylene, 1,3-butadiene).

As regards nitrogen oxides, the nitrogen component in kerosene is below the detection limit (1 ppm by mass or less) and so there are virtually no fuel-derived nitrogen oxides. Being elements derived from nitrogen in the air during combustion, they have not been taken into account.

The kerosene composition is a mixture of many and various compounds. It is extremely difficult to predict the exhaust-gas characteristics of oil-burning devices or the odour during combustion on the basis of the properties of the individual compounds or simply the distillation curves. But, by dint of intensive research, a kerosene composition has been found where it is possible to reduce the combustion odour further.

In the present invention, the range from initial boiling point to end point, in accordance with the atmospheric pressure distillation test method stipulated in JIS K2254, has been set at 140° C. to 300° C. because if the range is below 140° C. the flash point is outside the JIS standards (and gasoline taxes may apply). Also, if the range exceeds 300° C., the 95% distillation temperature and the Saybolt colour value of the kerosene, which are in the JIS standard, cannot be satisfied.

In order for the kerosene composition to display excellent heating performance, and for the exhaust-gas characteristics and odour to be further improved, the aforementioned conditions (1) to (5) are indispensable.

If the density of the kerosene composition is too high, the higher it is the more the combustion properties deteriorate. However, if the density is too low, there is a possibility that this will interfere with the heating properties. Normally the density is 0.81 g/cm³ or less or preferably 0.73 to 0.81 g/cm³, but 0.73 to 0.77 g/cm³ is particularly preferred.

The aromatic hydrocarbon content of the kerosene composition is set at 20% by volume or less. If it is too high, the higher it is the more the aromatic compounds such as benzene, toluene and xylene (referred to below as the aromatic component) in the exhaust gases increase, and the more the combustion properties deteriorate. Also, the unpleasant odour becomes too strong for some people, which is undesirable. The aromatic component in the kerosene composition is preferably 18% by volume or less, and 10% by volume or less is particularly preferred, but 5% or less by volume is even more preferred.

The fraction at 250° C. and above is 0 to 20% by volume, and preferably 0 to 18% by volume, and 0 to 12% by volume is particularly preferred.

If the value of the fraction at 250 to 300° C. is too high, the higher it is the more the combustion properties deteriorate, and the more the unburned hydrocarbons increase, so that it is preferred if the fraction at 250° C. and above is as low as possible.

Not only do the benzothiophenes and dibenzothiophenes, which are sulphur compounds, cause an increase in the sulphur oxides which are associated with an offensive odour at the time of combustion, but the hydrocarbons from the one or more aromatic compounds also increase.

Therefore, it is necessary to ensure that the sulphur content derived from the benzothiophenes and dibenzothiophenes is 0 to 50 ppm by mass and preferably 0 to 10 ppm and most preferably 0 to 5 ppm.

The benzothiophenes here refer to C1 benzothiophenes (1-ethylbenzothiophene, 2-ethylbenzothiophene, 3-ethylbenzothiophene, 4-ethylbenzothiophene), other alkylbenzothiophenes (including C2 benzothiophene, C3 benzothiophene, C4 benzothiophene, C5 benzothiophene), and dibenzothiophenes refer to dibenzothiophene, methyldibenzothiophenes (including 1-methyldibenzothiophene, 2-methyldibenzothiophene, 3-methyldibenzothiophene, 4-methyldibenzothiophene, C5 [di]benzothiophene), C1 alkyl[di]benzothiophenes (including ethyldibenzothiophene, propyldibenzothiophene), 4,6-dimethyldibenzothiophene, C2 dibenzothiophene, and other alkyldibenzothiophenes.

Also, the bromine index is an indication of the olefin compounds having double bonds. There are cases where these olefin compounds combine with carbon monoxide in the combustion process to form aldehydes, which have a noxious odour. Moreover, if there are few olefins, there is a link with an improvement in storage stability. Therefore, the olefin content of the kerosene composition is preferably 65 Br₂mg/100 g or less after conversion to bromine, but 40 Br₂mg/100g or less is particularly preferred, and 30 Br₂mg/100 g or less is still more preferred.

In the case of the smoke point, however, the more this value increases, the better the combustion properties, so that the unburned hydrocarbons in the exhaust gases are reduced, and the exhaust-gas properties and combustion odour are improved. Normally, if it is 21 mm or higher there will be no problems, but 23 mm or higher, or even better, 30 mm or higher, is preferred.

The kerosene composition of the present invention can easily satisfy the conditions of:

-   (a) Flash point 40° C. or higher; -   (b) Distillation characteristic (95% distillation temperature)     270° C. or lower; -   (c) Sulphur content 0.008% by mass or less; -   (d) Smoke point 21 mm or higher; -   (e) Copper strip corrosion (50° C., 3 hours) 1 or lower; -   (f) Saybolt colour +25 or higher;     under the test methods stipulated in JIS K2203.

Also, the above odour formula 10 Log {[4D+6(BT+DBT)+20A+Or+4T₂₅₀]/(0.01S) } is 84.0 or less, but 80 or less is preferred and 70 or less even more preferred. Still more preferable is 60 or less.

The lower the aromatic hydrocarbon component in the kerosene composition, and also the lower the density, the more the carbon component is reduced. This is also connected with a reduction in the amount of carbon dioxide emitted. But, because there is, at 1% or less, virtually no aromatic content in composition products prepared particularly by the method in which synthesis gas is obtained from natural gas or coal through partial oxidation or steam reforming, and this is then made into a long-chain alkyl hydrocarbon polymerised oil by a synthetic reaction such as the Fischer-Tropsch reaction, and then hydro-cracking and distillation are carried out to give the desired properties, it is possible to obtain compositions in which the hydrogen/carbon ratio is larger than in previous kerosenes, and so to reduce the carbon dioxide during combustion. A similar effect is obtained when the products from this gas and kerosene derived from crude oil are blended to reduce the aromatics.

The unburned hydrocarbons have a large influence during combustion. If the amount present is of the order of 300 ppm or less according to the concentration in the ambient air, there is no feeling of a strong odour, but it preferably should be 250 ppm or less, and even more preferably 200 ppm or less.

Since the kerosene composition is an agglomeration of many and various hydrocarbon and sulphur compounds, if, for example, only one of the above conditions (1) to (5) is satisfied, this may not mean any improvement in the exhaust-gas composition, and also, since the respective compounds are burned at the same time, it is difficult to speculate about the combustion properties and odour. However, as a result of investigation of the actual measurement of fuel properties and exhaust gases, it has been discovered that where said conditions are satisfied, satisfactory odour is achieved.

In accordance with the present invention there is also provided a kerosene composition as defined by the method of the present invention.

The present invention offers a kerosene composition with excellent heating performance, good combustion properties, good storage stability because of clean exhaust gases during combustion, low odour at ignition, during normal combustion or on extinction, and also a low concentration of carbon dioxide in the exhaust gases.

The kerosene base fuel may be additivated (additive-containing) or unadditivated (additive-free). If additivated, e.g. at the refinery or in later stages of fuel distribution, it will contain minor amounts of one or more selected additives. The (active matter) concentration of each such additional component in the additivated fuel composition is at a level required or allowed in the application is question.

The present invention will now be described in more detail by reference to the following Examples:

The methods of measuring the kerosene properties and of measuring the exhaust gases were as follows:

-   Density: JIS K2249; -   Aromatic component: JIS K2536 (Fluorescent indicator adsorption     method); -   Sulphur component derived from benzothiophenes and -   dibenzothiophenes: GCAED (Absolute calibration curve method against     an external standard using a gas chromatograph with an atomic     emission detector attached); -   250° C. to 300° C. fraction: JIS K2254, Distillation Test Method; -   Bromine index: JIS K2605.

To assess odour, the said kerosene composition was burned in an indoor fan heater (FH). The odour at ignition, during normal combustion and on extinction respectively was evaluated by 10 subjects. For the fan heater, a KD271D made by Mitsubishi Electric was used.

Three fuels with different characteristics were used. The names were masked and an odour evaluation based on the different fuels was carried out. The scores were 5 points for “no odour at all”, 4 points for “slight odour”, 3 points for “definite odour”, 2 points for “fairly strong odour” and 1 point for “strong odour”. For each fuel, the marks for, respectively, ignition, normal combustion and extinction were averaged, and fuels with an average of 3.5 or above were deemed to have passed.

Measurement of the unburned hydrocarbons in the exhaust gases from the fan heater, which are one of the elements of odour, was also carried out. Measurement of the unburned hydrocarbons was effected by a gas chromatograph fitted with an FID (flame ionisation detector) using samples of the exhaust gases from the heater taken at the louvre exit in cross tubes, in accordance with the JIS method. The measurement values in Table 1 record the summed values for unburned hydrocarbon values during ignition, normal combustion and extinction. It is considered that sulphur compounds and unregulated substances such as aldehydes, toluene, xylene have a strong influence on the components of odours, but since it is difficult to analyse the extremely small amounts relative to the unburned hydrocarbons accurately, as regards the amounts contained in exhaust gases, only the unburned hydrocarbons were recorded.

EXAMPLE 1

Natural gas was partially oxidised, and a heavy paraffin was synthesised by Fischer-Tropsch synthesis. A heavy paraffin oil was made and this was prepared by the SMDS (Shell Middle Distillate Synthesis) process in which naphtha, kerosene and light oil fractions are obtained. An n-paraffin/iso-paraffin oil mixture with the properties and composition shown in Table 1 was obtained. This was burned using the aforementioned fan heater, and an odour test was performed.

EXAMPLE 2

Unwashed straight-run kerosene distilled and separated from a Middle East crude oil in an atmospheric pressure distillation apparatus was subjected to a desulphurisation treatment using a cobalt-molybdenum catalyst with a liquid-space velocity of 4 hr⁻¹, a hydrogen-oil ratio of 150 Nm³/m³ feed, and a hydrogen partial pressure of 20 kg/cm². A kerosene with the properties and composition shown in Table 1 was obtained. This was burned using the aforementioned fan heater, and an odour test was performed.

COMPARATIVE EXAMPLE

Unwashed straight-run kerosene distilled and separated from a Middle East crude oil in an atmospheric pressure distillation apparatus was subjected to a desulphurisation treatment using a cobalt-molybdenum catalyst with a liquid-space velocity of 4 hr⁻¹, a hydrogen-oil ratio of 120 Nm³/m³ feed, and a hydrogen partial pressure of 15 kg/cm². A kerosene with the properties and composition shown in Table 1 was obtained. This was burned using the aforementioned fan heater, and an odour test was performed. TABLE 1 Test Comparative Method Example 1 Example 2 Example Density (g/cm³) JIS 0.7552 0.8016 0.8155 K2249 Sulphur content GCAED 0.05 3 42 (benzothiophenes) Method (ppm by mass) Sulphur content GCAED 0.05 6 28 (dibenzothiophenes) Method (ppm by mass) Smoke point (mm) JIS 50 25 22 K2537 Aromatics (% vol) JIS 0.1 17.6 22 K2536 Bromine index JIS 21.0 54.1 69.0 (Br₂ mg/100 g) K2605 Distillation (° C.) JIS K2254 Initial boiling point 160.5 153.0 160.5 10% 168.5 176.0 180.0 50% 184.0 208.5 211.0 90% 234.5 254.5 258.0 End point 253.5 273.5 282.5 250-300° C. fraction 2.5 13 16 (% vol) Odour formula (T 42.9 76.3 84.2 formula) value Unburned 165 295 306 hydrocarbons (ppm by mass) Odour score (average) 4.4 3.9 23 

1. A method of controlling the odour emitted by a kerosene composition such that it is below a specified level, which method comprises ensuring that said composition has the following properties: (1) the range from initial boiling point to end point, in accordance with the atmospheric pressure distillation test method stipulated in JIS K2254, is in the range of 140° C. to 300° C.; (2) the density is 0.81 g/cm³ or less; (3) the aromatic hydrocarbon content is 0 to 20% by volume; (4) the sulphur content derived from benzothiophenes and dibenzothiophenes is 0 to 50 ppm by mass; and (5) the fraction at 250° C. and above is 0 to 20% by volume.
 2. The method of claim 1 which comprises ensuring that said kerosene composition has a bromine index of 65 Br₂mg/100 g or less.
 3. The method of claim 1 which comprises ensuring that said kerosene composition satisfies the following odour formula (T formula): 10 Log{[4D+6(BT+DBT)+20A+Or+4T₂₅₀]/(0.01S) }≦_(—)84.0 where: Log is a natural logarithm; D is the density of the kerosene composition (g/cm³); BT is the sulphur content derived from benzothiophenes in the kerosene composition (ppm by mass); DBT is the sulphur content derived from dibenzothiophenes in the kerosene composition (ppm by mass); A is the aromatic hydrocarbon content of the kerosene composition (% by volume); Or is the bromine index of the kerosene composition (Br₂ mg/100 g after conversion to bromine); T₂₅₀ is the amount of distillate at 250° C. or more in the kerosene composition, in accordance with the atmospheric pressure distillation test method stipulated in JIS K2254 (% by volume); and S is the smoke point (mm); said odour formula being 80 or less.
 4. The method of claim 3 which comprises ensuring that the smoke point is 21 mm or higher.
 5. The method of claim 1 which comprises ensuring that the density is 0.73 to 0.81 g/cm³.
 6. The method of claim 1 which comprises ensuring that the aromatic hydrocarbon content is 18% by volume or less.
 7. The method of claim 1 which comprises ensuring that the sulphur content derived from benzothiophenes and dibenzothiophenes is 0 to 10 ppm by mass.
 8. The method of claim 1 wherein said benzothiophenes and dibenzothiophenes are selected from the group consisting of C1 benzothiophenes, other alkylbenzothiophenes, dibenzothiophenes, methyldibenzothiophenes, C1 alkyl[di]benzothiophenes, 4,6-dimethyldibenzothiophene, C2 dibenzothiophene, and other alkyldibenzothiophenes.
 9. The method of claim 1 which comprises ensuring that the fraction at 250° C. and above is 0 to 18% by volume.
 10. A kerosene composition as defined in claim
 1. 